U.S. patent number 6,648,951 [Application Number 09/946,460] was granted by the patent office on 2003-11-18 for waterfest, environmentally friendly inks adapted for point-of-sale ink-jet applications.
This patent grant is currently assigned to Hewlett-Packard Development Company, L.P.. Invention is credited to Xiaohe Chen, George M. Sarkisian, David Tyvoll.
United States Patent |
6,648,951 |
Chen , et al. |
November 18, 2003 |
Waterfest, environmentally friendly inks adapted for point-of-sale
ink-jet applications
Abstract
A waterfast, environmentally friendly ink-jet ink, is disclosed
comprising from 1% to 90% by weight of a first humectant selected
from the group consisting of glycerol, propanediol, and
combinations thereof; from 1% to 25% by weight of a second
humectant selected from the group consisting of ethylene glycol,
diethylene glycol, propylene glycol, and combinations thereof; from
1% to 20% by weight of a drying agent selected from the group
consisting of 1,2-hexanediol, 1,2-pentanediol, and combinations
thereof; from 0% to 20% by weight of 2-pyrrolidone; from 0.05% to
10.0% by weight of a waterfastness control dye selected from the
group consisting of azo-containing dyes and
phthalocyanine-containing dyes; and at least one additional dye
present at from about 1.0% to 10.0% by weight. If the waterfastness
control dye is an azo-containing dye, such dyes can include Direct
Red 227, Direct Red 254, Direct Yellow 86, and Acid Orange 7.
Alternatively, if the waterfastness control dye is a
phthalocyanine-containing dye, the nickel, copper or aluminum
phthalocyanines can be used.
Inventors: |
Chen; Xiaohe (San Diego,
CA), Tyvoll; David (La Jolla, CA), Sarkisian; George
M. (San Diego, CA) |
Assignee: |
Hewlett-Packard Development
Company, L.P. (Houston, TX)
|
Family
ID: |
26937619 |
Appl.
No.: |
09/946,460 |
Filed: |
September 4, 2001 |
Current U.S.
Class: |
106/31.47;
106/31.49; 106/31.51; 106/31.58 |
Current CPC
Class: |
C09D
11/30 (20130101); C09D 11/32 (20130101) |
Current International
Class: |
C09D
11/00 (20060101); C09D 011/02 () |
Field of
Search: |
;106/31.47,31.58,31.49,31.51 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Hewlett-Packard Journal, pp. 4-37 (May 1985). .
Hewlett-Packard Journal, pp. 6-56 (Aug. 1988). .
Hewlett-Packard Journal, pp 51-98 (Oct. 1988). .
Hewlett-Packard Journal, ppp 64-102 (Aug. 1992). .
Hewlett-Packard Journal, pp. 6-97 (Feb. 1994)..
|
Primary Examiner: Klemanski; Helene
Parent Case Text
Applicants claim priority to U.S. Provisional Patent Application
Ser. No. 60/245,980 filed Nov. 3, 2000.
Claims
We claim:
1. A waterfast, environmentally friendly ink-jet ink, comprising:
(a) from 1% to 90% by weight of a first humectant selected from the
group consisting of glycerol, propanediol, and combinations
thereof; (b) from 1% to 25% by weight of a second humectant
selected from the group consisting of ethylene glycol, diethylene
glycol, propylene glycol, and combinations thereof; (c) from 1% to
20% by weight of a drying agent selected from the group consisting
of 1,2-hexanediol, 1,2-pentanediol, and combinations thereof; (d)
from 0% to 20% by weight of 2-pyrrolidone; (e) from 0.05% to 10.0%
by weight of a waterfastness control dye selected from the group
consisting of azo-containing dyes and phthalocyanine-containing
dyes; and (f) at least one additional dye present at from about
1.0% to 10.0% by weight.
2. An ink-jet ink as in claim 1 wherein the waterfastness control
dye is an azo-containing dye.
3. An ink-jet ink as in claim 2 wherein the azo-containing dye is
selected from the group consisting of Direct Red 227, Direct Red
254, Direct Yellow 86, Acid Orange 7, and combinations thereof.
4. An ink-jet ink as in claim 3 wherein the waterfastness control
dye is Direct Red 227 and is present at from 0.1% to 1.0% by
weight.
5. An ink-jet ink as in claim 3 wherein the waterfastness control
dye is Direct Red 254 and is present at from 0.1% to 1.0% by
weight.
6. An ink-jet ink as in claim 3 wherein the waterfastness control
dye is Acid Orange 7 and is present at from 0.1% to 1.0% by
weight.
7. An ink-jet ink as in claim 3 wherein the waterfastness control
dye is Direct Yellow 86 and is present at from 0.1% to 1.0% by
weight.
8. An ink-jet ink as in claim 1 wherein the waterfastness control
dye is a phthalocyanine-containing dye.
9. An ink-jet ink as in claim 8 wherein the
phthalocyanine-containing dye is selected from the group consisting
of nickel phthalocyanine, aluminum phthalocyanine, copper
phthalocyanine, and combinations thereof.
10. An ink-jet ink as in claim 4 wherein the ink is green and the
at least one additional dye comprises about 1.5% to 3.5% of Acid
Blue 9 by weight and about 1.0% to 3.0% of Direct Yellow 86 by
weight.
11. An ink-jet ink as in claim 4 wherein the ink is blue and the at
least one additional dye comprises about 1.0% to 3.0% of Acid Blue
9 by weight and about 0.5% to 2.0% of Acid Red 52 by weight.
12. An ink-jet ink as in claim 5 wherein the ink is magenta and the
at least one additional dye comprises about 0.5% to 2.5% of Acid
Red 52 by weight.
13. An ink-jet ink as in claim 6 wherein the ink is orange and the
at least one additional dye comprises about 0.5% to 2.5% of Acid
Red 87 by weight and about 1.0% to 3.0% of Direct Yellow 86 by
weight.
14. An ink-jet ink as in claim 4 wherein the ink is red and the at
least one additional dye comprises about 0.5% to 2.5% of Acid Red
52 by weight and about 1.0% to 3.0% of Direct Yellow 86 by
weight.
15. An ink-jet ink as in claim 1 further comprising at least one
additive selected from the group consisting of buffers, corrosion
inhibitors, surfactants, biocides, polymers, puddling control
agents, pigments, and binders, and combinations thereof, and
wherein said additive present is present at from about 0.01% to 3%
by weight.
16. An environmentally friendly ink-jet ink composition for
point-of-sale applications having a dye load, comprising: (a) from
0.05% to 1.0% by weight of a waterfastness control dye selected
from the group consisting of azo-containing dyes and
phthalocyanine-containing dyes; and (b) at least one additional dye
present at from about 1.0% to 10.0% by weight, with the proviso
that the total dye load be at least 2% by weight, and wherein the
ink-jet ink is substantially non-toxic.
17. An ink-jet ink composition as in claim 16 printed on thermal
mechanical pulp (TMP) paper, and wherein the drytime when printed
on the thermal mechanical pulp paper is less than 300 msec.
18. A waterfast, environmentally friendly ink-jet ink, comprising:
(a) from 1% to 90% by weight of a first humectant selected from the
group consisting of glycerol, propanediol, and combinations
thereof; (b) from 1% to 25% by weight of a second humectant
selected from the group consisting of ethylene glycol, diethylene
glycol, propylene glycol, and combinations thereof; (c) from 1% to
20% by weight of a drying agent selected from the group consisting
of 1,2-hexanediol, 1,2-pentanediol, and combinations thereof; (d)
from 0% to 20% by weight of 2-pyrrolidone; (e) from 0.05% to 10.0%
by weight of a waterfastness control dye selected from the group
consisting of azo-containing dyes and phthalocyanine-containing
dyes; and (f) at least one additional dye present at from about
1.0% to 10.0% by weight, with the proviso that the first humectant,
the second humectant, and 2-pyrrolidone are present in combination
at from 30% to 90% by weight.
19. An ink-jet ink as in claim 18 wherein the first humectant, the
second humectant, and 2-pyrrolidone are present at from 40% to 60%
by weight.
20. An ink-jet ink as in claim 18 wherein the first humectant, the
second humectant, and 2-pyrrolidone are present at from 45% to 58%
by weight.
21. A waterfast, environmentally friendly ink-jet ink, comprising:
(a) from 1% to 90% by weight of a first humectant selected from the
group consisting of glycerol, propanediol, and combinations
thereof; (b) from 1% to 25% by weight of a second humectant
selected from the group consisting of ethylene glycol, diethylene
glycol, propylene glycol, and combinations thereof; (c) from 1% to
20% by weight of a drying agent selected from the group consisting
of 1,2-hexanediol, 1,2-pentanediol, and combinations thereof; (d)
from 0% to 20% by weight of 2-pyrrolidone; and (e) from 1.0% to
10.0% by weight of a dye, with the proviso that the first
humectant, the second humectant, and 2-pyrrolidone are present in
combination at from 30% to 90% by weight.
22. An ink-jet ink as in claim 21 wherein the first humectant, the
second humectant, and 2-pyrrolidone are present at from 40% to 60%
by weight.
23. An ink-jet ink as in claim 21 wherein the first humectant, the
second humectant, and 2-pyrrolidone are present at from 45% to 58%
by weight.
Description
FIELD OF THE INVENTION
The present invention is drawn to ink-jet ink compositions that are
environmentally friendly, reliable, fast drying, and waterfast for
use in ink-jet printers, particularly thermal ink-jet printers used
for point-of-sale (POS) applications.
BACKGROUND OF THE INVENTION
Thermal ink-jet printers provide an effective means of propelling
ink-jet inks onto various media including paper. These printers
accomplish this task by using resistive heater elements for heating
the ink to a boil, and propelling the ink through an overlying
orifice plate. Such printers are desirable for use for several
reasons. For example, thermal ink-jet printers have a relatively
fast throughput while being relatively inexpensive to run.
Additionally, these printers are relatively easy to use, and the
ink is easily replaced. Alternatively, piezo ink-jet printers can
similarly be used effectively.
When formulating inks for use with point-of-sale (POS)
applications, special challenges exist. Typical point-of-sale
machines, including cash registers, credit card receipt printers,
printers for checks, etc., print images that are often handled by
clerks and customers immediately after printing. For example, after
the printing of a receipt, a cash register worker must be able to
grasp the receipt and hand it to the customer immediately. To
accommodate immediate handling of such print jobs, some of the
typical print technologies used for POS applications have included
dot matrix impact printing and direct thermal printing. Though
these technologies are functional, each has certain limitations.
For example, dot matrix printing is often quite noisy, and direct
thermal printing can require special paper and lacks permanence
upon exposure to water, heat, or light. Additionally, neither
technology currently provides the ability to efficiently print in
multiple colors. Ink-jet printing would avoid these limitations,
but in order to be effective, very fast drying inks must be used.
In fact, due to the need to immediately handle printed papers as
described previously, even inks that may otherwise be considered
fast drying or waterfast may not be fast enough for POS
applications.
There are several properties that one can consider when determining
whether an ink is a good candidate for POS applications. Some of
these include rapid printing capability, low toxicity, infrequent
changing of ink cartridge, good decap, fast drying, at least equal
in print quality to other technologies in the field, and adequate
optical density. Of these properties, rapid printing capability,
low toxicity, and fast drying properties are particularly
important. Rapid print capabilities are accomplished by high
frequency printing. For example, about 1.5 kHz can implemented, or
even up to 3 kHz or greater can be effective for point-of-sale
applications. With respect to low toxicity, ink compositions that
are environmentally benign or have low toxicity are desired. This
is because point-of-sale prints will likely be handled extensively,
both by clerks and customers. Additionally, when discussing fast
drying, what is meant is the ability of an ink to dry in a fraction
of a second. In POS applications, the ink-jet ink should dry nearly
instantaneously, since upon completion of printing a receipt, it
will likely be immediately handled as described. Additionally,
prior to handling, the receipt generally touches a tear bar on the
printer above the print zone. Typically, this occurs approximately
300 msecs after printing a swath, and if the ink is not
substantially dry, the tear bar can also smear the ink. Thus, to
avoid smudges on the receipt and ink stains on the hands of the
clerk or the customer, the receipt must be essentially dry prior to
any opportunity for a person to handle the receipt, and preferably
prior to the receipt touching the tear bar of the printing machine.
With this in mind, it would be desirable to provide various ink-jet
ink compositions that are environmentally friendly and can be used
with POS apparatuses, taking in to account the challenges
associated with POS applications.
SUMMARY OF THE INVENTION
A waterfast, environmentally friendly ink-jet ink, is disclosed
comprising from 1% to 90% by weight of a first humectant selected
from the group consisting of glycerol, propanediol, and
combinations thereof; from 1% to 25% by weight of a second
humectant selected from the group consisting of ethylene glycol,
diethylene glycol, propylene glycol, and combinations thereof; from
1% to 20% by weight of a drying agent selected from the group
consisting of 1,2-hexanediol, 1,2-pentanediol, and combinations
thereof; from 0% to 20% by weight of 2-pyrrolidone; from 0.05% to
10.0% by weight of a waterfastness control dye selected from the
group consisting of azo-containing dyes and
phthalocyanine-containing dyes; and at least one additional dye
present at from about 1.0% to 10.0% by weight. If the waterfastness
control dye is an azo-containing dye, such dyes can include Direct
Red 227, Direct Red 254, Direct Yellow 86, and Acid Orange 7.
Alternatively, if the waterfastness control dye is a
phthalocyanine-containing dye, then nickel, copper, and/or aluminum
phthalocyanines can be used.
In one embodiment, the first humectant, the second humectant, and
the 2-pyrrolidone of the above composition can be present such that
a total weight percentage of these three components is from 30% to
90% by weight. In an alternative embodiment, when the total weight
percentage of these three components, i.e., first humectant, second
humectant, and 2-pyrrolidone, is greater than about 30%, only one
dye is required to be present.
Additionally, a fast drying, environmentally friendly ink-jet ink
composition for POS applications is disclosed having a dye load
comprising from 0.05% to 1.0% by weight of a waterfastness control
dye selected from the group consisting of azo-containing dyes and
phthalocyanine-containing dyes; and at least one additional dye
present at from about 1.0% to 10.0% by weight, with the proviso
that the total dye load be at least 2% by weight, and wherein the
ink-jet ink is substantially non-toxic.
A point-of-sale printing system is also disclosed, comprising a
non-toxic ink-jet ink; a point-of-sale (POS) paper configured for
accepting printed ink-jet ink; and an ink-jet pen configured for
rapid printing of the ink-jet ink onto the paper, wherein the
ink-jet ink printed on the paper has a drytime of less than 300
msec, and wherein the ink-jet ink exhibits good long-term decap
performance, i.e., on the order of multiple weeks.
DETAILED DESCRIPTION OF THE INVENTION
Before the present invention is disclosed and described, it is to
be understood that this invention is not limited to the particular
process steps and materials disclosed herein because such process
steps and materials may vary somewhat. It is also to be understood
that the terminology used herein is used for the purpose of
describing particular embodiments only. The terms are not intended
to be limiting because the scope of the present invention is
intended to be limited only by the appended claims and equivalents
thereof.
The singular forms "a," "an," and, "the" include plural referents
unless the context clearly dictates otherwise. Thus, for example,
reference to "an ink" includes reference to one or more of such
inks.
As used herein, "effective amount" refers to the minimal amount of
a substance or agent, which is sufficient to achieve a desire
effect. For example, an effective amount of an "ink vehicle" is the
minimum amount required in order to create ink, which will meet
functional performance and characteristic standards set forth
herein.
As used herein, "ink vehicle," refers to the vehicle in which dyes
are placed to form an ink. Ink vehicles are well known in the art,
and a wide variety of ink vehicles may be used with the ink
composition of the present invention. Such ink vehicles may include
a mixture of a variety of different agents, including without
limitation, surfactants, solvents, co-solvents, buffers, biocides,
viscosity modifiers, surface-active agents, and water. However, no
substance can be added to an ink-jet ink of the present invention
that would cause the ink-jet ink to become toxic.
"Waterfastness control dye" shall include any azo-containing dye or
phthalocyanine-containing dye which is functional to improve
waterfastness of an ink-jet ink composition. The dye used as the
waterfastness control dye cannot act as the second dye.
"Second dye" or "additional dye" can be any dye, regardless of
chemical structure, that is functional for imparting desired
coloration properties, as well as for imparting ultraviolet and
infrared absorbing properties. Even azo-containing dyes and
phthalocyanine-containing dyes that are functional also as the
waterfastness control dye can be used as the second dye, as long as
it is a different dye than that dye used for waterfastness control.
"Second dye" and "additional dye" also can include not only a
single dye, but a combination of two or more dyes.
"Environmentally friendly" or "non-toxic" shall mean any ink-jet
ink composition that can be ingested in small amounts and can be
discarded in wastewater streams without producing adverse health
effects, and is generally safe for use and contact by humans.
"Fast drying" shall mean that in less than 1 second, ink-jet inks
printed on typical POS papers will be dry to the touch, though less
than one half second is preferred, and less than 300 msec is most
preferred.
"Decap performance" refers to the tendency of inks, when present in
an ink-jet pen, to crust near the jetting orifice due to the
evaporation of solvents present in the ink. Ink-jet inks that
exhibit good long-term decap performance do not require the use of
a capping mechanism designed to prevent this type of crusting (as
is the case with most ink-jet inks) over reasonable periods of
time, e.g., several weeks or more.
Ink-jet ink compositions are disclosed herein that are reliable,
environmentally friendly, and are generally fast drying on the
order of 300 msec and less. Further, the ink composition exhibits
minimal puddling leading to improved print quality. With this in
mind, the ink-jet inks described herein comprise several
components. First, from about 1% to 90% by weight of a first
humectant must be present which is selected from the group
consisting of glycerol, propanediol, and combinations thereof.
These can exist in amounts of up to 90% because they are considered
to be totally non-toxic ingredients. Second, from 1% to 25% by
weight of a second humectant can also be present which is selected
from the group consisting of ethylene glycol, diethylene glycol,
propylene glycol, and combinations thereof. The reason these are
limited to 25% is because these substances are regulated by
European Union as hazardous above this amount. Next, from 1% to 20%
by weight of a drying agent selected from the group consisting of
1,2-hexanediol, 1,2-pentanediol, and combinations thereof can be
used to facilitate fast drying properties. These ingredients can be
added when the desire is to provide a very fast drying ink for
applications such as point-of-sale (POS) devices. From 0% to 20% by
weight of 2-pyrrolidone can also added. Again, the reason this
amount is limited to 20% is to comply with the EU regulations
related to toxicity of products. The colorant is provided in the
ink-jet ink by at least two dyes. One of the two dyes must be a
waterfastness control dye, such as an azo-containing dye or a
phthalocyanine-containing dye. Thus, from about 0.05% to 10.0% by
weight of a waterfastness control dye must be present. The second
dye or additional dye can be any dye functional for providing a
desired color. The second dye can be present at from about 1.0% to
10.0% by weight.
In one embodiment, the first humectant, the second humectant, and
the 2-pyrrolidone can be present in combination such that a total
weight percentage of these three components is from 30% to 90% by
weight. In a more preferred embodiment, the total weight percentage
of these three components can be from 40% to 60% by weight. In an
even more preferred embodiment, the total weight percentage of
these three components can be from 45% to 58% by weight. In yet
another embodiment, when the total weight percentage of these three
components, i.e., first humectant, second humectant, and
2-pyrrolidone, is greater than about 30%, only one dye of any
functional type is required to be present.
Appropriate azo-containing control dyes that can be used include
Direct Red 227, Direct Red 254, Direct Yellow 86, carboxylated Food
Black 286, carboxylated Food Black 287, and Acid Orange 7.
Additionally, any other combination of functional azo-containing
dyes can also be used. Alternatively, the waterfastness control dye
can be a phthalocyanine-containing dye, such as nickel
phthalocyanine, aluminum phthalocyanine, and/or copper
phthalocyanine.
As stated, the second dye can be any dye that is functional for
providing a desired color. Thus, even azo-containing dyes and
phthalocyanine-containing dyes can be used for the second colorant
as well. More generally, the second dyes can include any water- or
organic-soluble black, red, blue, green, orange, pink, yellow, or
other color. Examples include, but are not limited to, (1) blacks
including Food Black 2, Carta Black; Direct Black 168, carboxylated
Food Black 286, carboxylated Food Black 287; (2) reds including
Direct Red 9, and Acid Red 52; (3) yellows including Acid Yellow
23, Food Yellow 3; (4) blues including Acid Blue 9, Acid Blue 185,
Direct Blue 86, and FD&C Blue 1, to name a few. All of the dyes
mentioned are anionic dyes, and are typically supplied with sodium
counterions. However, the sodium counterions can be replaced with
lithium, potassium, ammonium, tetramethyl amine (tetramethyl
ammonium), triethanol amine (triethanol ammonium), or diethylene
amine cations, as disclosed, for example, in U.S. Pat. Nos.
4,685,968; 4,761,180; 4,786,327; and 4,810,292. The counterion
replacement may be performed by reverse osmosis, such as disclosed
and claimed in U.S. Pat. No. 4,685,968, or by ion exchange, such as
disclosed and claimed in U.S. Pat. No. 4,786,327.
To illustrate some embodiments of the present invention, several
green, blue, magenta, orange, black, and red ink-jet inks can be
formulated by using from 0.1% to 1.0% by weight of Direct Red 227
(DR227) as the waterfastness control dye. This is particularly
unique with respect to green and blue inks because red dyes are
typically not used in green and blue ink-jet ink formulations. For
example, a green ink-jet ink can be prepared by adding from 1.5% to
3.5% of Acid Blue 9 by weight and about 1.0% to 3.0% of Direct
Yellow 86 by weight to the Direct Red 227 dye described above.
Additionally, a blue ink-jet ink can be prepared by adding about
1.0% to 3.0% of Acid Blue 9 by weight and about 0.5% to 2.0% of
Acid Red 52 by weight to the Direct Red 227 dye. Next, a black
ink-jet ink can be prepared by adding about 3.0% to 5.0% of Food
Black 2 by weight to the Direct Red 227 dye. Additionally, a red
ink-jet ink can be prepared by adding about 0.5% to 2.5% of Acid
Red 52 by weight and about 1.0% to 3.0% of Direct yellow 86 by
weight to the Direct Red 227 dye.
In alternative embodiments, where different waterfastness control
dyes are used, an orange ink-jet ink can be formulated with from
0.1% to 1% of Acid Orange 7 (the azo-containing waterfastness
control dye) by weight with about 0.5% to 2.5% of Acid Red 87 by
weight and about 1.0% to 3.0% of Direct Yellow 86 by weight.
Additionally, a magenta ink-jet ink can be formulated with from
0.1% to 1% of Direct Red 254 (the azo-containing waterfastness
control dye) by weight with about 0.5% to 2.5% of Acid Red 52 by
weight.
A drying agent can also be present in the ink-jet formulations
described herein. Specifically, 1,2-hexanediol and/or
1,2-pentanediol can be added as a drying agent. Such an additive
can be more effective than simply adding increased amounts of
surfactants. While it is known that surfactants can decrease dry
time of inks, surfactants can also enhance the toxicity of some of
the other chemical components and exacerbate puddling of the ink.
Specifically, by adding 1,2-hexanediol and/or 1,2-pentanediol in
appropriate amounts, good dry time of less than about 300 msec and
low puddling can be realized. Additionally, these drying agents can
promote good frequency response in the area of about 3 kHz. Though
the use of a drying agent as described above is preferred over the
use of surfactants, surfactants can still be used in low amounts to
maintain low toxicity. If a surfactant is used to improve dry time,
then non-limiting examples of preferred surfactants such as those
available under the trade names TERGITOL.TM., SILWET.TM.,
DOWFAX.TM., DOWANOL.TM., AND SURFYNOL.TM. are appropriate. However,
as stated, these should only be added in low, non-toxic, and
non-puddling amounts.
In addition to the humectants, the drying agents, the
2-pyrrolidone, the surfactants, and the dyes describe herein,
additives selected from the group consisting of buffers, corrosion
inhibitors, biocides, polymers, puddling control agents, pigments,
binders, and combinations thereof, can be added to achieve desired
results. If such additives are added, from about 0.01% to 3% of
each by weight can preferably be used, though any effective amount
by weight can be added. However, it is important to note that the
ink-jet ink formulations described herein have been formulated to
provide non-toxic and environmentally friendly inks.
The ink-jet ink compositions described herein have several
advantages over many of the inks of the prior art. Because these
inks can be considered to be environmentally friendly, there is no
health hazard issue with respect to their use in any application.
Additionally, there is little or no waste disposal concern
associated with the ink-jet inks described herein. Though these
inks were formulated primarily with environmental considerations in
mind, other desirable properties have been realized. For example,
the inks have long term decap providing an ideal ink for
applications where there is no capping. Additionally, essentially
little or no kogation occurs with the inks of the present
invention. Kogation is a term describing the formation of a
non-soluble crystal residue that coats the inside of a firing
chamber. These crystals are typically formed upon the heating of
the ink during the firing process. The fact that the ink-jet inks
of the present invention are not subject to substantial kogation,
the print heads used with the inks of the present invention will
typically not wear out as quickly. Other advantages of the inks
described herein include their compatibility with thermal
mechanical pulp (TMP) paper. This is significant because TMP paper
is widely used in the POS receipt media market, but provides a
difficult substrate to obtain good waterfastness with typical
inkjet inks. By using this type of paper with the environmentally
friendly inks of the present invention, the print job can still be
legible after soaking the printed paper in water. Additionally, due
to the nature of ink-jet printing, multiple color POS print jobs
can be provided in a simple and easy manner. Thus, in comparison to
dot-matrix prints and direct thermal prints, a significant
advantage can be realized.
In a further detailed aspect of the present invention, an
environmentally friendly ink-jet ink composition for point-of-sale
applications is disclosed having a dye load comprising from 0.05%
to 1.0% by weight of a waterfastness control dye selected from the
group consisting of azo-containing dyes and
phthalocyanine-containing dyes; and at least one additional dye
present at from about 1.0% to 10.0% by weight, with the proviso
that the total dye load be at least 2% by weight, and wherein the
ink-jet ink is substantially non-toxic. Surprisingly, even if this
ink-jet ink is printed on thermal mechanical pulp (TMP) paper, or
other known POS papers, then a typical drytime can be less than 300
msec.
In yet another detailed aspect of the invention, a point-of-sale
printing system is disclosed, comprising a non-toxic ink-jet ink; a
point-of-sale (POS) paper configured for accepting printed ink-jet
ink; and an ink-jet pen configured for rapid frequency printing of
the ink-jet ink onto the paper, wherein the ink-jet ink printed on
the paper has a drytime of less than 300 msec, and wherein the
ink-jet ink exhibits good decap performance.
Though not required, the ink-jet inks described previously can be
used, such as, for example, ink-jet ink having effective amounts of
a waterfastness control dye and a second dye. Additionally, a
suitable POS paper that can be used is thermal mechanical pulp
(TMP) paper or tablet bond paper.
EXAMPLES
The following examples illustrate various formulations for
preparing the ink-jet ink compositions of the present invention.
The following examples should not be considered as limitations of
the invention, but should merely teach how to make the best known
ink formulations based upon current experimental data.
Example 1
A green ink-jet ink composition was prepared by admixing the
following ingredients by weight: 5% 1,3-propanediol, 24% ethylene
glycol, 15% 2-pyrrolidone, 9% 1,2-hexanediol, 2% Acid Blue 9 sodium
salt, 2.5% Acid Yellow 23 sodium salt, 0.5% Direct Red 227 sodium
salt, 0.3% MOPS, and the balance in water. The ink is printed onto
thermal mechanical pulp receipt paper and immersed in water for 24
hours. At the end of 24 hours, the printed characters are still
legible.
Example 2
A blue ink-jet ink composition was prepared by admixing the
following ingredients by weight: 11% glycerol, 20% diethylene
glycol, 18% 2-pyrrolidone, 5% 1,2-hexanediol, 2% Acid Blue 9 sodium
salt, 1% Acid Red 52 sodium salt, 0.4% Direct Red 227 sodium salt,
0.3% MOPS, and the balance in water. The ink is printed onto
thermal mechanical pulp receipt paper and immersed in water for 24
hours. At the end of 24 hours, the printed characters are still
legible.
Example 3
A magenta ink-jet ink composition was prepared by admixing the
following ingredients by weight: 10% glycerol, 20% ethylene glycol,
15% 2-pyrrolidone, 5% 1,2-hexanediol, 2% Acid Red 52 sodium salt,
0.5% Direct Red 254 sodium salt, 0.3% MOPS, and the balance in
water.
Example 4
An orange ink-jet ink composition was prepared by admixing the
following ingredients by weight: 10% glycerol, 15% ethylene glycol,
20% 2-pyrrolidone, 5% 1,2-hexanediol, 2% Food Yellow 3 sodium salt,
1% Direct Yellow 86 sodium salt, 0.5% Acid Orange 7 sodium salt,
0.3% MOPS, and the balance in water. The ink is printed onto
thermal mechanical pulp receipt paper and immersed in water for 24
hours. At the end of 24 hours, the printed characters are still
legible.
Example 5
A black ink-jet ink composition was prepared by admixing the
following ingredients by weight: 15% glycerol, 25% ethylene glycol,
10% 2-pyrrolidone, 7% 1,2-hexanediol, 0.7% Direct Red 227 sodium
salt, 4.5% Food Black 2 triethanolamine (TEA) salt, 0.3% MOPS, and
the balance in water. The ink is printed onto thermal mechanical
pulp receipt paper and immersed in water for 24 hours. At the end
of 24 hours, the printed characters are still legible.
Example 6
A red ink-jet ink composition was prepared by admixing the
following ingredients by weight: 5% glycerol, 20% ethylene glycol,
20% 2-pyrrolidone, 8% 1,2-hexanediol, 0.5% Direct Red 227 sodium
salt, 1.5% Acid Red 52 sodium salt, 2% Direct Yellow 86 sodium
salt, 0.3% MOPS, and the balance in water. The ink is printed onto
thermal mechanical pulp receipt paper and immersed in water for 24
hours. At the end of 24 hours, the printed characters are still
legible.
Example 7
The ink-jet ink compositions described in Examples 1 to 6 above
were loaded into the reservoir of a print cartridge having a nickel
orifice plate. The print cartridge was placed in a point-of-sale
(POS) ink-jet printer operating at a frequency of 3 kHz. The print
medium was thermal mechanical pulp receipt paper.
The pen was loaded to ink-out approximately 5 million 9-point font
characters. After printing a significant number of characters,
minimal ink puddling was present on the orifice plate, and no ink
puddle reached the pen electrical interconnect below the nozzle
plate. The resulting dry time was measured by mounting a small
horsehair brush 1.0 inches behind the pen such that the brush was
in contact with the printed medium. The pen was then printed with a
carriage speed of 5 inches per second. Table 1 below sets forth the
dry times for each ink tested.
TABLE 1 Ink used Dry time (Example No.; Color) (msec) 1; Green
<100.sup. 2; Blue 250 3; Magenta 200 4; Orange 200 5; Black 200
6; Red 100
Table 1 above shows that each of the ink-jet inks formulated in
accordance with the present disclosure had dry times at a fraction
of a second. In fact, each color had a dry time of less than 250
msec, which was better than the intended goal of less than 300 msec
of dry time.
While the invention has been described with reference to certain
preferred embodiments, those skilled in the art will appreciate
that various modifications, changes, omissions, and substitutions
can be made without departing from the spirit of the invention. It
is intended, therefore, that the invention be limited only by the
scope of the following claims.
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